1. Field of the Invention
The present invention relates to a power unit for a motorcycle including an internal combustion engine and a power transmission device that includes a continuously variable transmission and a hydraulically-operated clutch. The transmission includes a drive pulley provided on a drive pulley shaft adapted to receive rotational power transmitted from the engine, a driven pulley provided on a driven pulley shaft having an axis parallel to the drive pulley shaft and a belt wound around the drive pulley and around the driven pulley. The clutch is provided on at least one of the drive pulley shaft and the driven pulley shaft.
2. Description of Background Art
A power unit for a motorcycle is disclosed in Japanese Patent Laid-Open No. Sho 58-102828 wherein a start clutch for switching disengagement and engagement between a drive pulley shaft and a driven pulley shaft is provided on the drive pulley shaft of a continuously variable transmission.
In the power unit disclosed in Japanese Patent Laid-Open No. Sho 58-102828, a clutch control oil passage is adapted to direct working oil to the start clutch on the central side of the drive pulley shaft. A lubricating oil passage is provided that is adapted to lead lubricating oil toward the drive pulley on the drive pulley shaft so as to coaxially surround the clutch control oil passage. However, such a structure not only complicates the oil passage configuration but also needs to set the outside diameter of the drive pulley shaft to a relatively large size in order to ensure the rigidity of the drive pulley.